The Rite mandates that Catechumens go to the Rite of Election in order to enter the Period of Purification, which typically coincides with Lent.
If they don’t receive the Rite of Election, then they remain in the Catechumenate. For pastoral reasons, a Catechumen can be received into the Church without ever becoming Elect - but it seems that the writers of the document are not envisioning anything short of deathly illness - it would be up to the pastor to discern whether the person had a serious enough reason for missing the Rite of Election. I don’t know of any alternatives to the Rite of Election, and I’m pretty sure the Bishop only does it once a year.
Candidates remain Candidates throughout the process, from the Rite of Welcome through to final Initiation - the Calling to Full Communion doesn’t actually change their status, although it does make them known to the Bishop, and affirms that their journey so far has been fruitful.